The sacroiliac joint is the joint between the sacrum, at the base of the spine, and the ilium of the pelvis, which are joined by ligaments. It is a strong, weightbearing synovial joint with irregular elevations and depressions that produce interlocking of the bones.

Inflammation of this joint may be caused by sacroiliitis, one cause of disabling low back pain. With sacroiliitis, the individual may experience pain in the low back, buttocks and thighs, and may also have other symptoms of a rheumatic condition such as inflammation in the eyes or psoriasis. Another condition of the sacroiliac joint is called sacroiliac joint dysfunction (also termed SI joint dysfunction). While SI joint dysfunction also causes low back and leg pain, and results from inflammation of the sacroiliac joint, it differs from sacroiliitis in that its origin is a disruption in the normal movement of the joint (too much or too little movement in the joint).

Ligaments

Depending on the reference source cited, the anterior ligament may be described as just a thickening of the anterior joint capsule. The anterior ligament is certainly not as strong and well defined as are the posterior ligaments.
The posterior sacroiliac (SI) ligaments can be further divided into short and long. There is a very strong structure which is called the dorsal interosseous ligament. This structure is stronger than bone; such that the pelvis will fracture before this structure tears. There is much we do not know regarding pelvic ligaments. For example it is known that ligaments become loose during pregnancy in response to hormones, especially relaxin; to allow widening of the joints during the birth process. We do not know if the interoseous membrane has the same type of receptors as the ligaments, and the specific ligament nerves (called mechanoreceptors/nociceptors) of the SI joint have not been studied in detail. The long and short SI ligaments can be palpated and the tone of the ligaments can be compared from one side of the body to the other.

Stork Test

The Sacroiliac joint dysfunction (SI Joint Dysfunction) can be tested with the Stork Test.

With the patient standing and the examiner sitting behind, the examiner's left thumb is placed over the most posterior portion of the left posterior superior iliac spine (PSIS) and the right thumb overlying the midline of the sacrum at the same level.

Examiner asks the patient to flex the left hip and knee to a minimum of 90 degrees of the hip flexion. Imagine making an "L" with the leg and thigh.

A negative test finds the left thumb on the posterior superior iliac spine (PSIS) moving caudad (towards the tail) in relation to the right thumb on the sacrum.

The thumb placements are reversed, and the patient is asked to raise the right leg in similar fashion.

A positive finding occurs when the thumb on the PSIS moves cranially (towards the head) in relation to the thumb on the sacrum.

The findings of this test are correlated with those of the standing flexion test. The Stork test is more specific for SI joint Restriction.

If the patient has difficulty standing on one foot to perform the test, proprioceptive sensory motor balance deficit should be further evaluated.

Other tests

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These tests have to be interpreted very cautiously. There are many more tests available and passive motion tests can be performed to evaluate motion going through the structure. These are called spring tests. The Hesch Method is an extensive evaluation and treatment system that utilizes many spring tests applied to various parts of the bony pelvis. These are performed with various positions such as having the person lie prone, supine, sitting, side-lying, prone extension and prone flexion (also called Muslim Prayer Position).